Polymerizable composition and planographic printing plate precursor using the same

Abstract

There is provided a polymerizable composition comprising (A) a binder polymer, (B) a polymerizable compound having an unsaturated group, and (C) a diaryl iodonium salt having at least two electron-donating groups. The iodonium salt (C) preferably has three or more electron-donating groups. This polymerizable composition is useful as a recording layer of a negative type planographic printing plate precursor.

1. A polymerizable composition comprising a binder polymer, a polymerizable compound having an unsaturated group, and a radical polymerization initiator, the radical polymerization initiator comprising a diaryl iodonium salt having at least two electron-donating groups at each of the ortho and para positions on at least one of the aryl groups. 
     
     
       2. The polymerizable composition according to  claim 1 , further comprising a compound having an absorption maximum at 700 to 1200 nm. 
     
     
       3. The polymerizable composition according to  claim 1 , wherein the iodonium salt has three or more electron-donating groups. 
     
     
       4. The polymerizable composition according to  claim 1 , wherein the iodonium salt has four electron-donating groups. 
     
     
       5. The polymerizable composition according to  claim 1 , wherein the electron-donating group are alkoxy groups. 
     
     
       6. The polymerizable composition according to  claim 1 , wherein the diaryl iodonium salt having at least two electron-donating groups has a partial structure represented by the following formula (I): 
       
         
           
           
               
               
           
         
         wherein, in formula (I), R, R 1  and R 2  each independently represent an alkyl group or an aryl group. 
       
     
     
       7. The polymerizable composition according to  claim 1 , wherein the diaryl iodonium salt having at least two electron-donating groups has a partial structure represented by the following formula (I-ii): 
       
         
           
           
               
               
           
         
         wherein, in formula (I-ii), R, R 1 , R 2  and R 3  each independently represent an alkyl group or an aryl group. 
       
     
     
       8. The polymerizable composition according to  claim 1 , wherein a total of Hammett's values of substituents on an aryl skeleton of the diaryl iodonium salt is −0.56 or less. 
     
     
       9. The polymerizable composition according to  claim 1 , wherein the diaryl iodonium salt has an anion having a sulfonic acid group as a counter anion. 
     
     
       10. The polymerizable composition according to  claim 1 , wherein the binder polymer is an alkali-soluble resin. 
     
     
       11. The polymerizable composition according to  claim 1 , wherein the binder polymer includes a structural unit represented by the following formula (II): 
       
         
           
           
               
               
           
         
         wherein, in formula (II), R 1  represents a hydrogen atom or a methyl group; R 2  represents a linking group composed of 2 to 82 atoms selected from the group consisting of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms and sulfur atoms; A represents an oxygen atom or —NR 3 — wherein R 3  represents a hydrogen atom or a C 1-10  monovalent hydrocarbon group; and n is an integer of 1 to 5. 
       
     
     
       12. A planographic printing plate precursor comprising, on a support, a recording layer including the polymerizable composition of  claim 1 . 
     
     
       13. The planographic printing plate precursor according to  claim 12 , further comprising a protective layer provided on the recording layer. 
     
     
       14. The planographic printing plate precursor according to  claim 13 , wherein the protective layer comprises a filler. 
     
     
       15. The planographic printing plate precursor according to  claim 13 , wherein the protective layer comprises at least one inorganic filler and at least one organic filler. 
     
     
       16. The planographic printing plate precursor according to  claim 13 , wherein the protective layer includes a lower protective layer that includes an inorganic layered compound and an upper protective layer that includes a filler. 
     
     
       17. The planographic printing plate precursor according to  claim 12 , wherein the support is an aluminum support. 
     
     
       18. The planographic printing plate precursor according to  claim 13 , wherein the protective layer comprises polyvinyl alcohol.